This isn’t an issue with Nitro but rather a problem with Tahoe Public Beta which affects Nitro.
I noticed in Beta 1 that any RAW image from my Lumix camera would not open correctly in Apple Photos. In fact it would simply be a black rectangle. My solution was to switch to shooting RAW+JPEG while away on vacation and for the ones already taken I used Nitro to auto enhance as a batch before trying to view them.
Now with Tahoe Beta 2 those RAW only images simply crash Photos and even Nitro cannot deal with them. It looks as if Apple have somehow mucked up the RAW file handling in Tahoe and I suspect this will be a problem for Nick going forwards. Btw the public beta of iPadOS did exactly the same thing.
I’m back on Sequoia now (Tahoe was only on one of my Macs) and will not rush to Tahoe until I know it works.